1. Human Genetic Disorders
Harmful or Beneficial?

2. Human Genetic Disorders
Mutations are key
DNA change  change in alleles
Chromosomal errors 
nondisjunction
Deletion, inversion, translocation

3. Disorders may be… In germ cells or somatic cells Dominant or recessive
Autosomes or Sex linked

4. Many inherited disorders in humans are controlled by a single gene
Most such disorders are caused by autosomal recessive alleles
Examples: cystic fibrosis, sickle-cell disease
Normal Dd
Normal Dd
PARENTS D D
Eggs
Sperm DD
Normal d d Dd
Normal
(carrier) Dd
Normal
(carrier)
OFFSPRING dd
Deaf
Figure 9.9A

5. A few are caused by dominant alleles
Examples: achondroplasia, Huntington’s disease
Figure 9.9B

6. Table 9.9

8. Tracking Traits & Prediction
Before mating
Genetic screening - karyotype
Punnets
Pedigree analysis

10. Family pedigrees are used to determine patterns of inheritance and individual genotypesDd
Joshua
Lambert Dd
Abigail
Linnell D_
John Eddy ? D_
Hepzibah Daggett ? D_
Abigail
Lambert ? dd
Jonathan Lambert Dd
Elizabeth
Eddy Dd Dd dd Dd Dd Dd dd
Female
Male
Deaf
Figure 9.8B
Hearing

11. Genetic testing Fetal cells can be obtained through amniocentesis
Amniotic fluid withdrawn
Centrifugation
Amniotic fluid
Fluid
Fetal cells
Fetus (14-20 weeks)
Biochemical tests
Placenta
Several weeks later
Figure 9.10A
Uterus
Cervix
Karyotyping
Cell culture

12. After fertilization Amniocentesis Chorionic villi sampling
Protein tests/biochemical tests via urine samples
Ultrasound (sonogram)
**Genetic counseling for all**

13. Some biochemical tests
Chorionic villus sampling obtains fetal cells for karyotyping
Fetus (10-12 weeks)
Several hours later
Placenta
Suction
Karyotyping
Fetal cells (from chorionic villi)
Some biochemical tests
Chorionic villi
Figure 9.10B

14. Uultrasound (sonogram)
Figure 9.10C, D

15. Risks to consider: Harm to baby Harm to mother
Invasive, risk of miscarriage
Harm to mother
Invasive, risk of infection
Ethical, moral, personal decisions